From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EE1B4C27C76 for ; Sat, 28 Jan 2023 11:19:33 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pLjEn-0000Up-Qj; Sat, 28 Jan 2023 06:19:13 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pLjEm-0000U0-70 for qemu-devel@nongnu.org; Sat, 28 Jan 2023 06:19:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pLjEk-0004Uk-E5 for qemu-devel@nongnu.org; Sat, 28 Jan 2023 06:19:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674904749; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=M+kApOH39KWGgEI4OumPMgAM39KwNFnoreiz5z3Ag5I=; b=IGUSn9JtspwInkaIg8pg1mW92Ot5na1OOTUSaQsKaOIMQ7okKp+mBA3wcuS78t6YjhSOc2 zUu4jV+FqzWE+TPeYHjbLYIpFzX0YszDkvSRYpBCdX4I56KTVKED5icBwjJLkUxkwgJke9 vRH12nmygELT7dF79WH1Pf/vueTrwL4= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-655-OQCGxBifOF2RJIyVaJm44g-1; Sat, 28 Jan 2023 06:19:06 -0500 X-MC-Unique: OQCGxBifOF2RJIyVaJm44g-1 Received: by mail-wm1-f72.google.com with SMTP id h9-20020a1ccc09000000b003db1c488826so6200729wmb.3 for ; Sat, 28 Jan 2023 03:19:05 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=M+kApOH39KWGgEI4OumPMgAM39KwNFnoreiz5z3Ag5I=; b=m1o1faQe4Jpfp3WoxX3KNojRW9C2LOf1gSUpr4KFo/K3c1UIMhFPaqI7HTpP5SeuHT YjqzS7ubry4yuX7EbNjt4LhidsaqpBb8smZeZpX0pf5lGHwZhUKEQfFjQky881lS09m1 h/+i7gxR9kLJ1HknxMeXBYT1KTfE07m7OqHGBkO4VB9GzY8Fr7MymbmbcsUKSu5E2VrL Bp1Vj6wygRpGWQKCD5He9JzevN4OJLKWKdUdvbHT0RcvlokdoVVqODtseFJJ+4O64ySP 1zdq2I6vJy7hvpWtTxAnHKGpcb2NJfO0ThW8hTeA+us85+l4chEi6sp/z7sdZYeYTbef eRCw== X-Gm-Message-State: AFqh2kra18lAFHxmAdOm89wRMN0GVUIAvyEfos6oUXVHKM7RqtHsh/uE 4fSFKj3UM3BWcJt3EbvCaIJFLYzxnPtM4rUdb8TNHtzbu6mN0JAXp4BcoOl2vXW9/b7eFecZuMK 2PHlJG38Zv6aafRg= X-Received: by 2002:a05:600c:c12:b0:3da:28a9:a900 with SMTP id fm18-20020a05600c0c1200b003da28a9a900mr40848117wmb.41.1674904744529; Sat, 28 Jan 2023 03:19:04 -0800 (PST) X-Google-Smtp-Source: AMrXdXsywxNmvfGwBRPLzcmC7vssP0ZsINOaSKGFpCB2hi6pA6vHF9kqvIg//hPQmOWUWromS8N6rA== X-Received: by 2002:a05:600c:c12:b0:3da:28a9:a900 with SMTP id fm18-20020a05600c0c1200b003da28a9a900mr40848099wmb.41.1674904744226; Sat, 28 Jan 2023 03:19:04 -0800 (PST) Received: from redhat.com ([2.52.20.248]) by smtp.gmail.com with ESMTPSA id l21-20020a05600c4f1500b003b47b80cec3sm11600364wmq.42.2023.01.28.03.19.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 28 Jan 2023 03:19:03 -0800 (PST) Date: Sat, 28 Jan 2023 06:19:00 -0500 From: "Michael S. Tsirkin" To: Xuan Zhuo Cc: qemu-devel@nongnu.org, Jason Wang Subject: Re: [PATCH 2/3] virtio: struct VirtQueue introduce reset Message-ID: <20230128061558-mutt-send-email-mst@kernel.org> References: <20230128071724.33677-1-xuanzhuo@linux.alibaba.com> <20230128071724.33677-3-xuanzhuo@linux.alibaba.com> <20230128050411-mutt-send-email-mst@kernel.org> <1674902469.9566288-2-xuanzhuo@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1674902469.9566288-2-xuanzhuo@linux.alibaba.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Sat, Jan 28, 2023 at 06:41:09PM +0800, Xuan Zhuo wrote: > On Sat, 28 Jan 2023 05:22:05 -0500, "Michael S. Tsirkin" wrote: > > On Sat, Jan 28, 2023 at 03:17:23PM +0800, Xuan Zhuo wrote: > > > In the current design, we stop the device from operating on the vring > > > during per-queue reset by resetting the structure VirtQueue. > > > > > > But before the reset operation, when recycling some resources, we should > > > stop referencing new vring resources. For example, when recycling > > > virtio-net's asynchronous sending resources, virtio-net should be able > > > to perceive that the current queue is in the per-queue reset state, and > > > stop sending new packets from the tx queue. > > > > > > Signed-off-by: Xuan Zhuo > > > --- > > > hw/virtio/virtio.c | 8 ++++++++ > > > include/hw/virtio/virtio.h | 3 +++ > > > 2 files changed, 11 insertions(+) > > > > > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > > > index 03077b2ecf..907d5b8bde 100644 > > > --- a/hw/virtio/virtio.c > > > +++ b/hw/virtio/virtio.c > > > @@ -2030,6 +2030,12 @@ void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index) > > > { > > > VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev); > > > > > > + /* > > > + * Mark this queue is per-queue reset status. The device should release the > > > + * references of the vring, and not refer more new vring item. > > > + */ > > > + vdev->vq[queue_index].reset = true; > > > + > > > if (k->queue_reset) { > > > k->queue_reset(vdev, queue_index); > > > } > > > @@ -2053,6 +2059,8 @@ void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index) > > > } > > > */ > > > > > > + vdev->vq[queue_index].reset = false; > > > + > > > if (k->queue_enable) { > > > k->queue_enable(vdev, queue_index); > > > } > > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > > > index 1c0d77c670..b888538d09 100644 > > > --- a/include/hw/virtio/virtio.h > > > +++ b/include/hw/virtio/virtio.h > > > @@ -251,6 +251,9 @@ struct VirtQueue { > > > /* Notification enabled? */ > > > bool notification; > > > > > > + /* Per-Queue Reset status */ > > > + bool reset; > > > + > > > uint16_t queue_index; > > > > > > > Reset state makes no sense. It seems to imply queue_reset > > in the spec. And for extra fun there's "reset" in the pci > > proxy which means "virtio_queue_reset is in progress" - I have no > > idea what uses it though - it is not guest visible. First what is it? > > It actually means "queue has been reset and not has not been enabled since". > > So disabled_by_reset maybe? > > > In fact, when reading this, the queue has not been reset, > so prepare_for_reset? Makes it sound like it's some kind of temporary state where it is not - it will stay like this until enabled. As this makes no practical difference that it is set to early, just set it later for consistency. > > > > Second this hack helps make the change minimal > > so it's helpful for stable, but it's ugly in that it > > duplicates the reverse of enabled value - we don't really > > care what disabled it in practice. > > > > With the fixups above I can apply so it's easier to backport, but later > > a patch on top should clean it all up, perhaps by adding > > "enabled" in VirtQueue. We should also get rid of "reset" in the proxy > > unless there's some way it's useful which I don't currently see. > > > > I have some confusion, I don't understand what you mean. > > Why did we remove the "reset" in the proxy? We did not but we should. Why we should remove "reset" in the proxy? Because guest can never read it as != 0: case VIRTIO_PCI_COMMON_Q_RESET: if (val == 1) { proxy->vqs[vdev->queue_sel].reset = 1; virtio_queue_reset(vdev, vdev->queue_sel); proxy->vqs[vdev->queue_sel].reset = 0; proxy->vqs[vdev->queue_sel].enabled = 0; } break; from guest's POV reset is atomic and so does not need a variable to track state. > I agree to rename the "reset". > > Thanks. > > > > > > > > unsigned int inuse; > > > -- > > > 2.32.0.3.g01195cf9f > >